Giving Equine Herpes Virus the Wobbles

Work aimed at developing a new vaccine to protect
against abortigenic and neurological equine herpes virus (EHV) has begun
at veterinary charity, the Animal Health Trust (AHT).

Dr Neil Bryant of the AHT, who is leading the research, said:
“EHV
is a major welfare concern for horses and foals and causes emotional,
as well as financial strains, on horse owners and breeders around
the world. It can strike any horse at any time so a vaccine will be
of global welfare benefit to all horses, including the Thoroughbred
and sports horse breeding industries, and would help control this
serious and sometimes fatal disease.”

As a viral infection, EHV can cause respiratory disease, abortion
or fatal illness in new born foals and neurological disease in adult
horses, with signs ranging from slight wobbliness through to complete
paralysis. The disease can strike any horse at any time because the
virus, like other herpesviruses (such as the cold sore virus in humans),
becomes dormant within most horses early in their life. It then re-emerges
when the animal is later stressed such as when transported or mixed
with new horses. A seemingly healthy pregnant mare may suddenly, and
without warning, abort her unborn foal or may show signs of respiratory
disease including mild fever, coughing and discharge from the nose.
A horse which appears fit and well may suddenly show abnormalities
when walking and within hours may be unable to stand.

Despite the
potential severity and impact of outbreaks, there is still no vaccine
that is licensed to protect against the neurological form of the disease
and abortions still occur in highly vaccinated horse populations.
Protection afforded by existing vaccines currently in use is sub-optimal,
and this was highlighted by the 2016 abortion storm in Hertfordshire
in fully vaccinated animals.

Dr Bryant said:
“We have become aware
of a pressing need for progress towards a new and improved EHV-1 vaccine.
Just last month, the AHT was again called upon to work with the racing
industry and affected parties in dealing with confirmed cases of EHV-1
abortion in premises in Yorkshire and Suffolk.”

Identifying this need
has led the veterinary charity to establish and host meetings of
an Equine Industries EHV Vaccine Steering Group. The steering group,
chaired by Professor
Joe Brownlie of the RVC, includes world-renowned
experts on both human and equine herpes viruses from a number of
research establishments. After careful consideration of the published
literature and extensive scientific discussions, the group has agreed
that the most appropriate way forward is for the AHT to design a
modified live virus (MLV) vaccine.

Trustees of the AHT, Professor David Silk and David Ellis, along with
Professor Sidney Ricketts and Professor Joe Brownlie, have been incredibly
influential in pulling the project together. Their efforts have helped
inspire a large group of funders from the Thoroughbred world to support
and fund this important vaccine research. Thanks to significant support
from Alborada Trust, EBM Charitable Trust, Horserace Betting Levy Board
and the Racing Foundation, Paul Mellon Estate, Thompson Family Charitable
Trust, Coolmore Ireland, Newsells Park Stud, Thoroughbred Breeders’ Association
and Juddmonte Farms, the AHT has begun its five-year research programme.

Dr
Kirsten Rausing DL, of the Alborada Trust, said:
“My trustees and I proudly
support world-class veterinary research. The Alborada Trust has made a
major commitment to this new and very important project. Alongside the
other major funders, we are all determined to tackle the suffering and
loss caused by EHV though effective vaccination.”

Professor Silk added:
“I have been very happy to have been associated with this research project.
Funding for it has been truly international with contributions coming from
horsemen based in Europe, the US, and the Gulf States. This international
funding has supplemented the very significant donations the AHT has received
from our UK supporters. I am certain that our quest to develop an effective
vaccine will succeed.”

Dr Bryant added:
“We’re at the beginning of a very
exciting and potentially ground-breaking vaccine development. Through our
research, we will construct different viruses with attenuating mutations
and assess their suitability as MLVs. We hope our findings will enable
further development by vaccine manufacturers in creating an effective vaccine
to protect against the serious clinical signs induced by EHV-1.”